The present invention relates to a device and method that can be used to enhance circumferential or radial dispersion of reactants, minimize diversity in products and reduce reactor fouling by minimizing the radial variation in concentration in a plug flow reactor.
Plug flow reactors can be used for a wide range of reactions. Reactions can be based on chemical or physical reactions to form compounds, polymers, small molecule materials, blends, alloys, biologically active species, or biological species. Chemical reactions include both organic and inorganic reactions. Blends and alloys can also be made in a plug flow reactor for example by physically mixing components. The blends or alloys may comprise, for example, polymers mixed with inorganics such as silica, carbon black, or clay forming nanocomposite type materials or other reinforced materials.
Plug flow reactors may be used with various polymer synthesis methodologies including any step-growth polymerization mechanisms, for example, polycondensations; or chain-growth polymerization mechanisms, for example, anionic, cationic, free-radical, living free radical, coordination, group transfer, metallocene, ring-opening, and the like. (See Odian, “Principles of Polymerization” 3rd Ed., Wiley-Interscience, 1991, NY, N.Y). The synthesis of homopolymers; random copolymers; block copolymers; star-branched homo-, random, and block copolymers; and end-functionalized polymers is possible by using appropriate polymerization techniques.
Various types of polymers can be prepared from different monomeric materials, the particular type formed being generally dependent upon the procedures followed in contacting the materials during polymerization. For example, random copolymers can be prepared by the simultaneous reaction of the copolymerizable monomers. Block copolymers are formed by sequentially polymerizing different monomers. The ability to form different types of polymers through control of the polymerization is referred to generally as controlled architecture. Controlled architecture polymers are designed with various types or variations of morphology including: linear, branched, star, combination network; variations in composition including: block copolymer, random copolymer, homopolymer, graft copolymer, tapered or gradient copolymer; and/or variations in functionality including: end, site specific, telechelic, multifunctional, and macromonomers.
Variation in local concentrations of reactants within plug flow reactor systems leads to greater diversity in the products. For example, the products of any given polymerization reaction are a mixture of polymer molecules of different molecular weights related to the length and composition of the individual chains. Living anionic polymerization reactions are very fast and exothermic. Therefore the polymer chains will tend to grow longer in localities within a plug flow reactor where the concentration of reactant monomer is relatively higher. The resulting disparity in lengths of the different polymer chains increases the polydispersity index (PDI), a reflection of poor uniformity between individual polymer chains produced by the reaction.
Block copolymers as an example of controlled architecture, are known to self assemble into 3-dimensional morphologies, which are tunable by variations and constituent block sizes and overall molecular weights. In order to achieve a uniform morphology, all of the polymer chains should have a uniform length in composition. This uniformity is reflected in the polydispersity index (PDI). The uniformity also relates and controls the order/disorder transition (crystalline/amorphous properties) of the block copolymer system. Compositional gradients also adversely affect block copolymer properties. For example, in the synthesis of a block copolymer with a 50/50 mole % composition, there could be a statistical mixture of compositions around that desired point which average to 50:50, although composed of a broader distribution, for example 45:55, 46:54, or 60:40 etc. In products with controlled architecture, variance is preferably minimized.
A plug flow reactor equipped with a single point delivery system can be plagued by reactor fouling, due to concentration gradients in 3D space. This increases downtime and increases the need to clean the reactor, thus decreasing production rates and productivity. Fouling can occur due to solubility differences associated with high and low molecular weight systems. This effect can be especially prevalent in the synthesis of amphiphilic block copolymers or polymer containing highly polar segments. These materials tend to micellize and exhibit interesting or challenging solubilities and adhesion to materials (i.e. the glass reactor and metal paddles). Examples of amphiphilic blocks are high acid content polymers which show decreased solubility in non-aqueous solvents and vinyl pyridine-containing block copolymers where high vinyl pyridine content block copolymers display limited solubility in typical polymerization solvents such as cyclohexane and toluene.